TNF and rheumatoid arthritis: Among pro-inflammatory cytokines, TNF-α is the master element of inflammation (McInnes and Schett, 2011), and IL-6 and IL-1β are downstream mediators of TNF-α (Zheng et al., 2014), which together play a critical role in mediating synovitis and joint destruction in RA (Xin et al., 2014).